nonLinearSolver.h

Go to the documentation of this file.

// ---------------------------------------------------------------------
//
// Copyright (c) 2017-2025  The Regents of the University of Michigan and DFT-FE
// authors.
//
// This file is part of the DFT-FE code.
//
// The DFT-FE code is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the DFT-FE distribution.
//
// ---------------------------------------------------------------------
//
 
 
 
#ifndef NonLinearSolver_h
#define NonLinearSolver_h
 
 
#include "headers.h"
 
namespace dftfe
{
  //
  // forward declarations
  //
  class nonlinearSolverProblem;
 
  /**
   * @brief Base class for non-linear algebraic solver.
   *
   * @author Sambit Das
   */
  class nonLinearSolver
  {
    //
    // types
    //
  public:
    enum ReturnValueType
    {
      SUCCESS = 0,
      FAILURE,
      LINESEARCH_FAILED,
      MAX_ITER_REACHED,
      RESTART
    };
 
    //
    // methods
    //
  public:
    /**
     * @brief Destructor.
     */
    virtual ~nonLinearSolver() = 0;
 
    /**
     * @brief Solve non-linear algebraic equation.
     *
     * @param problem[in] nonlinearSolverProblem object.
     * @param checkpointFileName[in] if string is non-empty, creates checkpoint file
     * named checkpointFileName for every nonlinear iteration.
     * @param restart[in] boolean specifying whether this is a restart solve.
     * @return Return value indicating success or failure.
     */
    virtual ReturnValueType
    solve(nonlinearSolverProblem &problem,
          const std::string       checkpointFileName = "",
          const bool              restart            = false) = 0;
 
    virtual void
    save(const std::string &checkpointFileName) = 0;
 
 
  protected:
    /**
     * @brief Constructor.
     *
     */
    nonLinearSolver(const unsigned int debugLevel,
                    const unsigned int maxNumberIterations,
                    const double       tolerance = 0);
 
 
  protected:
    /**
     * @brief Get tolerance.
     *
     * @return Value of the tolerance.
     */
    double
    getTolerance() const;
 
    /**
     * @brief Get maximum number of iterations.
     *
     * @return Maximum number of iterations.
     */
    unsigned int
    getMaximumNumberIterations() const;
 
    /**
     * @brief Get debug level.
     *
     * @return Debug level.
     */
    unsigned int
    getDebugLevel() const;
 
 
    /// controls the verbosity of the printing
    const unsigned int d_debugLevel;
 
    /// maximum number of nonlinear solve iterations
    const unsigned int d_maxNumberIterations;
 
    /// nonlinear solve stopping tolerance
    const double d_tolerance;
  };
 
} // namespace dftfe
 
#endif // NonLinearSolver_h